Loop antenna



Feb. 22, 1955 w. FARBANlsH 2,702,860

LOOP ANTENNA Filed Au 21, 1953 wove siqnql Receiver WALTER FARBANISH Loop Inducfnce core Plofes ond l2 De9rees Fl G HIs ATToRNEY.

Un1ted StateS Patent Loof ANTENNA vva1fef Eafbanfsh, Ch1cago, 111., SS1gnof fo Zenff11 1ad1o cofpofaf1on, a cofpofafion of 111111ois AppHcafion Augusf 21, 1953, seffa1 No. 375,7o1

4 c1a1mS. (CL Zs033.o7)

ThiS invention felateS to a new and 0npfoved 1oop antenna opefable ovef a fange of ffeqflencieS; the an tenna Stfuctufe iS pafticu1af1y valuable when en1ployed if1 an appafatuS fof feceiving SignalS in the standafd bfoadcast band extending ffom appfoxinlately S40 to 1600 kilocyc1es, and accofding1y W111 be descfibed in that connection.

It has 1ong been a pfactice of fadio manufactufefS to incofpofate, WithiI1 the con0neS of the cabinet StfuctUfe a SUitable and e1fective feceiving antenna. The advantages of 1oop antennaS afe we11 known howevef, the space fequifements of known types of 1oop antefLnaS he pfeSenfed a Sefious design 1ifnitation in view of the poblic demand fof feducHon in Size of ceftain types of fadio fe ceivefs. This pub1ic deInand togethef with a desife on the paft of fadio manufactufefS to feduce the amount of Inatefia1 fequifed to n1anufactufe an individua1 feceivef has inffoduced nlany pfoblefnS, among which is that of pfoviding a cofnpact yet e1fective bl1i1tin 1oop antennap ()ne type of antenna vvhich haS found genefa1 acce tance conSiSts of a pancake type of coi1 cofnpfiSing a plufality of concentfic tufns of conductive vife lying in a coInnon plane cenlented to a Inounting boafd of low loss high dielecffic fnatefiaL Anothef anfenna in genefal uSe con Sists of a fod of cylindef of feffofflagnetic Inatefia1 and a he1ica1 coi1 coInpfiSing a lafge nUInbef of tnfns of condnctive Wife Wound afound the cofe. The above-fefeffed to antennas have both been used SatiSfactofily iI1 n1ay feceivefS. Howevef, these two antennas and genefany a11 antennaS of a siIni1af type have the con1- fnon disadvantage that it iS viftua11y ifnpoSSib1e to Inanufactufe co11S of 1oopS in InaSS pfoduction to eXact Speci fication, and it haS thefefofe been customafy pfactice to tfim of fune the 1oop of each feceivef aftef aSSefnbly of the 1oop Wi111 the chaSSis. In an antenna of the pancake type, this adjusonent iS 11SIlal1y accoInplished by hand and iS made by incfeaSing of decfeaSing the numbef of tufnS of conductive Wife. In the type of antenna con1pfising a he1ica1 coi1 Wound afound a feffoInagnetic cofe, adiuSonont may be n1ade by Withdfawing a poftion of the cofe ffom the 1ie1d of the coi1 in a long1- fudinal difect1on fo effect the desifed change in in ductance. ThuS, the tfin1n1ing of known typeS of loop antennaS fequifes e1t11ef a tedioI1S cutandtfy hand o )efa tion to achieve the optiInUfI1 indoctance by pfogfesSive fen1ova1 of ffactiona1 poftionS of wife tufnS, of the pfovision of a ceftain affloLInt of cabinet space fequifed fof no othef pufpose than to pefn1it paftia1 vvithdfawa1 of a feffofflagnetic Cofe ffofn Vvithin the 11eld of the antenna 1oop.

11 iS an obiect of thiS inventiof1, thefefofe, to pfovide a new and ifnpfoved 1oop antenna Stf11ctI1fe which nlay be encofnpaSSed vvithin the cabinet of a waveSigna1 fe ceivef to occupy a nlinin1un1 of space.

1t iS a fufthef obiect of this invention fo pfovide a nevv and ifnpfoved 1oop antenna Stfuctufe in which adiustnlent of tfifnfning of the inductance Inay be accon1- p1iShed Vvithout the necesSity of peffoffning tediouS hand opefationS and Without effecting a change in the phySica1 size of the antenna.

1t is a cofo11afy obiect of thiS i11vention to pfovide a 1oop anfenna sffuctnfe having peffonnance chafactefistics oofnpafab1e Wit11 t11ose achieved w1th pfovioUSly k11ovvn 1oop antennas Wh11e eecting a Inatefia1 conSefvation of both Space and 1flatefiaL 1f is an additional obiect of thiS invefltion fo pfovide a new and 11Tlpfoved 1oop antenna stf11ctufe Which is 8 Z,70z,800 Pafenfed Feb. 22, 1955 sin1p1e and expedienf to constfuct and convenient and eco non1ica1 to olanufactufe.

In acCofdance vvith the invention, a 1oop antenna Stfoctufe opefab1e ovef a fange of ffequencies con1pfises a, honow dielectfic coi1 fofm and at 1east two 11at cofe plates. The cofe p1ates afe each SubStantially fectangulaf in ofoSS Section and afe moUnted Within the coi1 fofm in spaced 1ongitudina1 a1ignInent with each ofhef, and at leaSt one of the cofe plateS is fotafab1e abollt a Se1fconfained axis With feSpect to the othef cofe p1afe. ^A 11elica1 coi1 compfiSing a p1I1fa1ity of cloSely adjacent nTutua11y inSulafed tIlfnS of conductive vife encon1pasSeS the co11 fofff1 and the cofe plateS, vvhefeby the inductance of the antenna nlay be adjusted bh fofating one of the cofe platos vith feSpect fo 1he o ef.

The featufes of the pfeSent i11vention vhich afe be- 1ieved to be nove1 afe Set fofth With pafticulafity in the appended claifns. The invention, togethef with fufthef obiectS and advantages thefeof, Inay beSt be undefStood, hovvevef, by fefefence fo the foHowing deScfiption taken in connection With the accofnpanying dfawing, in the sevefal 11g11feS of which like fefefence nufffefa1S indicato 1ike elementS, and in Which= Figufe 1 is a pefspective view of an antenna stfuctufe accofding to the invention;

Figufe Z is a sectiona1 view taken a1ong 1ine ZZ of Figufe 1; and

Figufe 3 iS a gfaphica1 fepfesentation of an opefating chafactefiStic of the antenna of FigUfeS 1 and Z.

The antenna i11uStfated in pefSpective in Figufe 1 compfises a honovv co11 fofm 10 of dielectfic nlatef1a1, Such aS Bake1ite; the coil fofIn Sefves aS a Suppoff fof the fefnaindef of the antenna StfuctI1fe. A1though coi1 fofm 10 iS Shown aS a Sing1e continuouS die1ectfic cyHndef, it fnay confofm to any Suitab1e cfoss Section. Two cofe p1ateS 11 and 12, of 11at of fectangulaf croSS Section and conSiSting eSSentially of a feffon1agnetic n1atefiaL pfefefab1y fflolded of eXtfuded sintefed feffite sI1ch aS pfeSent1y nlanufactufed by the Spfague E1ectfic Company and cofnn1efcia11y known as Feffoxcube, afe Inounted Within coi1 fofIn 10 in 1ongitudina1 aHgnnlent and afe S aced by a dielectfic diSc 13 which Sefves aS a fneanS of pfe venth]g 1ongitudina1 abutfnent of fhe cofe plateS but P Inay be oInftted of feplaced by any othef n1eanS fof accompliShing the Same pufpoSe. The length L and width W of each of the plateS 11 and 1Z afe SUbstantia11y gfeafef than ifS t11icknesS D. one of 1he Cofe plafeS iS fotatab1e about a Se1fc0ntained axiS vVith fespect to the othef cofe plafe; fof eXan1ple, cofe p1ate 1Z fnay be SecUfed by gluing of in any othef convenient fnannef to coil foffI1 10 vv1111e cofe p1ate 11 iS IT1efe1y inSefted in Sf111g but II1ovable engagefnent vvith coil fofn1 10 fo be fotatable about itS own longifudina1 aXiS, of if deSifed both cofe p1ateS lTlay be fotatable abont fespective se1f contained aXeS. In the pfefeffed embodiment Cofe p1ates 11 and 12 afe contained vVithin coi1 fofm 10, and cofe 1)1ate 11 fotates about the cofnn1on 1ongitudinal aXis of coi1 foffn 10. Cofe plate 11 is Shown in dotted out- 1ine in a position ffon1 hofizonta1 to indicate the de gfee of adiustInent a1lowed by thfS Stfuctufe.

Two connectin lu s 15 are affiXed to the coil form and )fovide meanS fof electfica11y connect1ng the antenna to a wave-Signa1 feceivef 16 Such aS a sfna11 tab1e nTode1 of poftable fadio feceivef, hefe indicated in block ou1 1iI1e, A helica1 coi1 17 encompaSSeS Co11 fofn1 10 and cofe p1ates 11 and 1Z, and the teffflina1S of coi1 17 afe feSpective1y e1ectfica11y connected to the two lugS 15. Coi1 17 compfises a plufa1ity of c1oso1y adjacent mu tllal1y inSulated tufnS of conductive vVife enCoInpassing coi1 fofn1 10 and cofe plates 11 and 1Z- ThiS insu1ated fe1ationship nlay be achieved by adequate1y Spacing the tufnS, of pfefefab1y by n1aking the co11 ffom an inSu1a tioncovefed vife of high condUctivity AS Seen Inofe cleaf1y in the cfosS-Sectiona1 view of Figufe 2, heHca1 coi1 17 includeS a 1afge numbef of tufnS which lie closely adjacent to each ofhef and which afe vound in SUch a fnannef aS to confofIn SubSfantia11y to the cifcuJ]fefentia1 Sufface of coi1 foffn 10. Coi1 fonn 10, aS fnofe c1eaf1y indicated in this vievv, has an inSide d1ametef SubStantia11y equa1 in width to the cofe plates 

